Choose a beast capable of being a mount that is no larger than Large with a challenge rating of 1/4 or lower. Add half your proficiency bonus to the beast’s AC, attack rolls, and damage rolls, as well as to any saving throws and skills it is proficient in. Its hit point maximum equals its normal maximum or four times your fighter level, whichever is higher.

Mount Action Economy

We purposely left the mount’s action economy out of the rules. I think that it should be up to the individual GM as to how that works. The beastmaster ranger got a lot of flak for not “feeling” right exactly because of this. Consult your GM on what is best for your group.

Knight’s Challenge

At 7th level, as a bonus action, you can challenge a single target within 60’. Against this target, you gain your Charisma bonus to attack rolls for 1 minute. You must rest before using this ability again.

Charging Blow

At 10th level, if you make a melee attack while mounted against a non-mounted opponent and move at least 30 feet, you deal +1d8 weapon damage on your next attack.

Banner

At 15th level, your name and banner are symbols of hope and righteousness. This banner inspires and empowers those around you to greatness. All allies within 60 feet gain a bonus to attack rolls and saving throws equal to half your proficiency bonus as long as you are not reduced to 0 hit points or otherwise incapacitated.

Dauntless Charge

At 18th level, whenever you make an attack while mounted against a non-mounted opponent, and move at least 30 feet, you gain advantage on your next attack. In addition, your mounted attacks score a critical hit on a roll of 19 or 20.